Conventionally, there is multi-protocol label switching (MPLS) that enables the operation of a network based on end-to-end paths a network including a plurality of nodes by introducing the concept of a label switch to an internet protocol (IP) network. In addition, not only for the IP network, as a technique for operating a network based on various kinds of paths in an autonomous and distributed manner, generalized multi-protocol label switching (GMPLS) is used. The GMPLS operates a time division multiplexing (TDM) network such as a synchronous digital hierarchy (SDH)/synchronous optical network (SONET) in an autonomous and distributed manner. In addition, as another example, the GMPLS operates a wavelength switching network or an optical transport network (OTN) in an autonomous and distributed manner.
In the MPLS or the GMPLS, as a technique for signaling through an end-to-end path, a resource reservation protocol-traffic engineering (RSVP-TE) is used. Specifically, in the MPLS or the GMPLS, a route from a start node to an end node is calculated by using topology information of a network that is collected by open shortest path first extended for traffic engineering (OSPF-TE). Then, in the MPLS or the GMPLS, the RSVP-TE is autonomously transmitted and received between nodes. Accordingly, in the MPLS or the GMPLS, the communication of a main signal is started by stretching a label switched pass (LSP) on the end-to end. Such a technique has been discussed in the internet engineering task force (IETF), the optical internetworking forum (OIF), the international telecommunication union (ITU), and the like, and a standardization operation thereof is in progress. (see, for example, International Publication Pamphlet No. WO 2004/102903, Japanese Laid-open Patent Publication No. 2008-60755, Japanese Laid-open Patent Publication No. 2008-85642, and International Publication Pamphlet No. WO 2005/101759.)
However, according to a conventional technique, in a network that includes a plurality of nodes, there is a problem in that an error occurs in the selection of a route relating to data transmission. Specifically, according to the conventional technique, in a case where there is a restriction on the connection destination of a route relating to data transmission, it is difficult to calculate a route to which the restriction is applied, and accordingly, an error occurs in the selection of a route relating to the data transmission.
FIG. 25A is an explanatory diagram illustrating a conventional problem occurring in a case where there is a restriction on the connection destination. In FIG. 25A, each node of Node A to Node D, for example, includes ports #1 to #8, and, in a network including the nodes, a cost value is assigned to each route connecting the ports between nodes. The cost value represents a data transmission state in a route up to a node as a link destination and, for example, is a value corresponding to a parameter such as a band, a speed, a distance, or a time relating to communication. FIG. 25A illustrates that a smaller cost value represents a route that is more optimal than other routes. For the calculation of a route, for example, a Dijkstra algorithm, a Bellman-Ford algorithm, or the like may be used, which acquires a shortest route as a constrained shortest path first (CSPF). In the calculation of a route using such an algorithm, a route having the minimum sum of assigned cost values is calculated. Here, it is assumed that all the bands are in a vacant state in each port, and each node maintains topology information that is advertised by the OSPF-TE. Here, the number of ports may be different from node to node.
In FIG. 25A, in Node A and Node D, routes each having a restriction on the connection are denoted by broken lines. Specifically, there are restrictions on the connection destinations between ports #3-1 to #3-4 and port #4 of Node A, and between port #4 and ports #3-1 to #3-4 of Node D. In the description of FIG. 25A, for example, a case will be described in which a start point is port “#1” of Node A and an end point is port “#1” of Node D in a network including a plurality of nodes from Node A to Node D. In addition, it is assumed that the calculation of a route is performed by Node A.
In the above-described configuration, Node A calculates a route in which the sum of assigned cost values is the minimum. As the route selected as above, a route is selected in the order of “port “#1” and “#2” of Node A”, “ports “#1” and “#4” of Node B”, and “port “#4” of Node D”. As a result, in the network illustrated in FIG. 25A, a route denoted by a dotted line is selected. Here, in Node D, connection destinations that can be connected to port #4 are ports #3-1 to #3-4. Thus, according to a conventional technique, in the network illustrated in FIG. 25A, it is difficult to select a route reaching port #1 of Node D as the end point, so that an error occurs. In addition, the route that is to be originally selected is a route, which is denoted by a solid line illustrated in FIG. 25A, passing through port #3 of Node B.
Accordingly, a supervisor is aware of the presence of a node having a restriction on the connection destination within the network and sets information that selects a route passing through a specific port. FIG. 25B is a diagram illustrating an example in which information used for selecting a route passing through a specific port. In the example illustrated in FIG. 25B, a supervisor, for example, sets information used for selecting a route passing through port #2 of Node A and port #2 of Node D. For example, the information used for selecting a route passing through a specific port may be referred to as “Include designation”. In FIG. 25B, ports that are designated for “Include designation” are denoted by black circles. Node A, as illustrated in FIG. 25B, selects a route that includes “ports “#1” and “#3” of Node B” based on “Include designation”.
However, originally, one of the advantages of the MPLS or the GMPLS is to autonomously calculate a route without involving a supervisor therein. However, when a system is configured such that the supervisor-has to set “Include designation” and additional maintenance step will be added to a conventional one for considering the setting of “Include designation” to a specific port of a specific node. In addition, “Include designation” may be set when a restriction is newly set in a network in which there has been originally no restriction. When a restriction is newly set, a maintenance sequence for performing setting not using the GMPLS is required, compared to a conventional case.